1. Field of the Invention
The present invention relates to a novel process for the preparation of unique (meth)acrylic/glutarimide copolymers, as well as to intermediate polymers useful in such preparation.
2. Description of the Prior Art
(Meth)acrylic resins possess numerous useful properties, such as transparency, resistance to the environment, in particular to solvents, abrasion resistance, rigidity, good mechanical properties, and the like. These properties render them well suited for use in the optical fields, as materials for high performance optical circuits, optical communication over short distances and optical sensors, and in the fields of utility components, as automotive components, decorative components, components of electrical household appliances, and the like. Unfortunately, these polymers have a heat distortion temperature which is low and which restricts their uses.
Accordingly, a wide variety of processes have been proposed to this art which are intended to raise the glass transition temperature Tg, including that process which comprises introducing imide groups into the (meth)acrylic (co)polymer.
U.S. Pat. No. 2,146,209 describes an imidification process in which a (meth)acrylic acid polymer or an ester thereof is reacted with a primary amine in the presence or absence of a solvent at a temperature ranging from 140.degree. to 200.degree. C.
EP-A-0,200,530 describes and claims a process which comprises two stages. The first stage comprises the polymerization of methacrylic acid and/or methyl methacrylate; the second stage comprises the addition of ammonia or of a primary amine to the reaction mixture, maintained at a high temperature (150.degree.-300.degree. C.), to provide a glutarimide polymer.
Indeed, in all of the prior art processes the amine reagent is incorporated during the modification reaction. The degree of salification of the intermediate products is poorly controlled and, thus, the final products do not always exhibit constant properties. Furthermore, it is difficult to modify the working conditions of such processes in order to target both the constitution of the desired final polymers and their glass transition temperature Tg.